1. Field of the Invention
The present invention relates to an intake manifold in a multi-cylinder internal combustion engine wherein the manifold is designed to super-charge an air-fuel mixture by an inertia effect. The present invention also relates to a connecting method for branch pipes of such an intake manifold.
2. Description of the Related Art
An inertia charge intake manifold includes a surge tank and a plurality of branch pipes for connecting the surge tank to the cylinder head of a multi-cylinder internal combustion engine. Each of the branch pipes needs to be relatively long for utilizing the inertia effect of the gas flow for supercharging. Further, all of the branch pipes need to be substantially equal in length for equalizing the inertia effect within the respective branch pipes.
JP-U-1(1989)-99965 discloses an inertia charge intake manifold which is made of a metal such as aluminum or suitable alloy. The intake manifold includes a surge tank located remote from the cylinder head of a multi-cylinder internal combustion engine, and a plurality of relatively long branch pipes connecting the surge tank to the cylinder head. The surge tank is located remote from the cylinder head to provide a long path for arranging the relatively long branch pipes without sharply bending.
However, since the surge tank is located remote from the cylinder head, the engine combined with the intake manifold becomes inevitably bulky. Further, difficulty arises in supporting the surge tank on the engine particularly in view of the fact that the surge tank itself must support other intake components such as a throttle body or carburetor which is relatively heavy. Indeed, a large tough support bracket is necessary for this purpose, which results in an increase of cost and weight. Still further, since the conventional manifold is made of aluminum for example, the branch pipes tend to have rather rough inner surfaces which may cause the flow resistance within the branch pipes to become unfavorably high.